This invention relates to a process for the preparation of pyrazolopyridine derivatives.
Pyrazolopyridine derivatives of formula (Ia) 
and pharmaceutically acceptable derivatives thereof in which:
R0a and R1a are independently selected from H, halogen, C1-6alkyl, C1-6alkoxy, or C1-6alkoxy substituted by one or more fluorine atoms;
R2a is H, C1-6alkyl, C1-6alkyl substituted by one or more fluorine atoms, C1-6alkoxy, C1-6hydroxyalkyl, SC1-6alkyl, C(O)H, C(O)C1-6alkyl, C1-6alkylsulphonyl, C1-6alkoxy substituted by one or more fluorine atoms; and
R3a is C1-6alkyl or NH2;
are disclosed in WO 00/26216 (Glaxo Group Limited), unpublished at the priority date of the instant application.
Pyrazolopyridine derivatives of formula (Ib) 
and pharmaceutically acceptable derivatives thereof in which:
R0b and R1b are independently selected from H, halogen, C1-6alkyl, C1-6alkoxy, or C1-6alkoxy substituted by one or more fluorine atoms;
R2b is halogen, CN, CONR4bR5b, CO2H, CO2C1-6alkyl, or NHSO2R4b;
R3b is C1-6alkyl or NH2; and
R4band R5b are independently selected from H, C1-6alkyl, phenyl, phenyl substituted by one or more atoms or groups (selected from halogen, C1-6alkyl, C1-6alkoxy, or C1-6alkoxy substituted by one or more fluorine atoms), or together with the nitrogen atom to which they are attached form a saturated 4 to 8 membered ring;
are disclosed in WO 00/52008 (Glaxo Group Limited), also unpublished at the priority date of the instant application.
As described in WO 00/26216 and WO 00/52008, the compounds of formulae (Ia) and (Ib) are potent and selective inhibitors of COX-2 and, as such, are of use in human and veterinary medicine, particularly in the treatment of the pain (both chronic and acute), fever and inflammation of a variety of conditions and diseases. Such conditions and diseases are well known in the art and include arthritis, such as rheumatoid arthritis; and degenerative joint diseases, such as osteoarthritis.
Several processes for the preparation of the compounds of formulae (Ia) and (Ib) are respectively disclosed in WO 00/26216 and WO 00/52008, inter alia the thermal rearrangement of an azirine in 1,2,4-trichlorobenzene at reflux.